President Jimmy Carter recently became the first U.S. president to publicly oppose Keystone XL — and now he has come out swinging at the kings of climate denial: the Koch brothers.

In a world where climate champions are few and far between, this is a unique opportunity to point to Jimmy Carter — a living portrait of the leadership we need on climate — and embolden other progressive leaders to follow suit.

Sign the petition to thank Jimmy Carter for exposing the climate denial machine.